Mobile application development has grown significantly in recent years with the rise of smartphones. There are many mobile operating systems and platforms that each have their own approach. Java ME and BREW are virtual environments that provide a common development platform but have limitations. Symbian and S60 are mature operating systems that dominate the market but have complex development environments. The iPhone platform is very popular but tightly controlled by Apple. Android provides an open alternative with a full software stack based on an optimized Java virtual machine. It allows for modular application components and uses intents to facilitate interaction. Overall, mobile development remains fragmented but platforms are working to standardize and open up to developers.